Diagnostic value of thyroid antibodies

Helicobacter pylori infection is markedly increased in patients with autoimmune atrophic thyroiditis

Infection by viral or bacterial pathogens has been suspected in playing a role in the development of autoimmune thyroid disease. Because Helicobacter pylori might be involved in the development of nongastrointestinal conditions such as rosacea, ischemic heart disease, and diabetes mellitus, we evaluated the prevalence of H. pylori infection in patients with autoimmune thyroid disease. Fifty-nine patients with autoimmune thyroid disease were included: autoimmune atrophic thyroiditis (n=21), Hashimoto's thyroiditis (n=18), and Graves' disease (n=20). Twenty patients with nontoxic multinodular goiter served as controls for nonautoimmune thyroid disease, and 11 patients with Addison's disease served as controls for nonthyroid endocrine autoimmune disease. The levels of anti-H. pylori immunoglobulin G (IgG) were determined, and a radiolabeled urea breath test were performed. The prevalence of H. pylori infection was markedly increased in the patients with autoimmune atrophic thyroiditis (85.7%), compared with the controls with nontoxic multinodular goiter (40%) and Addison's disease (45.4%). Infection by H. pylori resulted in increased levels of gastrin, pepsinogen I, and pepsinogen II in the H. pylori-positive groups, compared with the H. pylori-negative groups. A positive linear regression was found between the levels of microsomal autoantibodies and those of anti-H. pylori IgG in patients with autoimmune atrophic thyroiditis (n=21; r=0.79; p < 0.01). Finally, and although the overall prevalence of H. pylori infection was not increased, the anti-H. pylori IgG levels and the results from the breath test were higher in the patients with Graves' disease and Hashimoto's thyroiditis patients than in the controls. Clearly, the prevalence of H. pylori infection is increased in autoimmune atrophic thyroiditis and results in abnormalities of gastric secretory function. The strong relation between the levels of anti-H. pylori IgG and the levels of microsomal antibodies suggests that H. pylori antigens might be involved in the development of autoimmune atrophic thyroiditis or that autoimmune function in autoimmune atrophic thyroiditis may increase the likelihood of H. pylori infection.

Interpretation of thyroid function tests

The development of radioimmunoassays over the past 20 years has expanded our knowledge of thyroid physiology and improved our management of thyroid disease. The use of these tools in neonatal screening for congenital hypothyroidism alone has reduced the incidence of mental retardation in the industrialized world. Based on an accurate physical examination, the judicious use of immunoassays for thyroxine, triiodothyronine, and thyrotropin and the use of thyroglobulin and thyroid microsomal antibodies will allow the general physician to confidently delineate common thyroid disorders in the great majority of patients. The additional use of an ultrasensitive thyrotropin assay, thyroid scans, and fine-needle aspiration biopsy will complete the accurate diagnosis of the great majority of thyroid diseases. The ultrasensitive thyrotropin assay may become the universal thyroid function test. The major pitfalls in the use of these tests lies in the variable effect chronic illness has on the most frequently used tests: thyroxine and triiodothyronine. Tests for these thyroid hormones, which in the relatively well outpatient are highly accurate, may in the ill, hospitalized patient become very misleading.

Disturbance of circadian rhythms in severely brain-damaged patients correlated with CT findings

Twelve patients aged 3-14 years with severe brain damage of prenatal, perinatal or postnatal origin were studied for 2-4 days regarding the circadian rhythms of sleep and wakefulness, body temperature and blood cortisol levels. Six patients had developed a disorder in the circadian rhythm of sleep and wakefulness. The circadian rhythm of body temperature was maintained in 11 of the patients and was little disturbed compared to those of sleep and wakefulness and cortisol levels. The three overt rhythms of circadian activity were not necessarily disturbed simultaneously, which does not contradict the multiple oscillatory theory of the human time-keeping system. CT findings suggested that the brain-stem plays a more important role than the cerebral hemispheres in the regulation of human circadian rhythms.

Antibodies to the thyroid gland and to the thyrotrophin receptor in African and Indian thyrotoxic patients

Sixty two thyrotoxic patients, 34 African and 28 Indian, were studied in order to assess the prevalence of thyroid antibodies and TSH binding inhibitory activity (TBI): 45 had Graves' disease and 17 had toxic nodular goitres. Microsomal and thyroglobulin antibodies were positive more often in Indian than in African patients with Graves' disease (microsomal 52% vs 37.4%, P less than 0.05; thyroglobulin 38.1% vs 4.2%, P less than 0.001). Patients with toxic nodular goitres had a lower prevalence of positive microsomal antibodies (P less than 0.01), but not of thyroglobulin antibodies (P = 0.1) when compared with patients with Graves' disease. TBI activity measured by a radioreceptor assay was positive in 43 of the 45 (95%) patients with Graves' disease and only 1 of the 17 patients (5.9%) with toxic nodular goitre. It thus appears that TBI activity is a sensitive marker in the diagnosis of Graves' disease and that there is a lower prevalence of thyroglobulin and microsomal antibodies in African patients compared with Indian patients.

A high prevalence of thyroglobulin autoantibodies in adults with and without thyroid disease as measured with a sensitive solid-phase immunosorbent radioassay

Sera from 228 patients with thyroid disease and 140 healthy subjects without clinical or biochemical evidence of thyroid disease, were tested using a sensitive solid-phase immunosorbent radioassay (RIA) and a passive hemagglutination test (TRC test) for thyroglobulin antibodies (Tg-ab). With the RIA technique, Tg-ab was found in 27% of the controls (36% of the women and 15% of the men), whereas only 0.7% of them were Tg-ab positive with the TRC test. All individuals with primary hypothyroidism were Tg-ab positive with the RIA, compared with only 56% with the TRC test. Tg-ab (RIA) were found in 43/53 (81%) of the patients with toxic diffuse goiter, and in 30-40% of the patients with toxic nodular goiter, toxic adenoma, atoxic goiter, and thyroid carcinoma, the TRC test being positive in 10-17% of these patients. The high prevalence of Tg-ab in the healthy population suggests that subclinical thyroiditis is more frequent than has been assumed from antibody measurements made with less sensitive methods, and is in agreement with the prevalences reported from autopsy studies.

A new sensitive immunosorbent radioassay for the detection of circulating antibodies to polypeptide hormones and proteins

A solid-phase immunosorbent radioassay for the detection of circulating antibodies to protein hormones is described. The assay is based on the binding of the homologous 125I-labelled antigen to the antibodies which are then bound to anti-IgG antibodies covalently coupled to Sepharose. It can easily be applied as a complement to any radioimmunoassay for the detection of circulating antibodies to the ligand measured. The assay system avoids falsely elevated values due to interference of high serum concentrations of the antigen. The assay was applied to measure antibodies to FSH, LH, TSH, GH, prolactin, insulin and thyroglobulin (Tg). Among patients with chronic thyroiditis Tg antibodies were found in 100% of the sera. In diffuse toxic goitre 73% of the patients had detectable Tg antibodies. Insulin antibodies were present in 82% of the sera from patients with insulin treated diabetes. No antibodies were found against the other protein hormones tested.

Changes of circulating thyroid autoantibody levels during and after the therapy with methimazole in patients with Graves' disease

The changes occurring in the levels of circulating thyroid microsomal antibody (M-Ab) and antithyroglobulin antibody (Tg-Ab) during antithyroid drug therapy were studied in 32 patients receiving methimazole for Graves' disease. M-Ab was determined by competitive binding radioassay and Tg-Ab by a sandwich radiometric method. Before treatment 25 subjects (78.1%) had abnormally elevated (greater than or equal to 75 U/ml) M-Ab levels. A more than 30% reduction of M-Ab concentration with respect to the pretreatment value was found in 16 (64.0%) of these patients within the first 3-5 months of therapy, in 23 (92.0%) within 8-11 months and in 21 (84.0%) at the end of treatment (16-18 months). No change was found in the 7 patients with initial M-Ab levels less than 75 U/ml. The reduction of M-Ab was more pronounced in the patients with good control of thyrotoxicosis than in those who were still hyperthyroid or were rendered hypothyroid during treatment. Twenty-three patients were followed after completion of the course of methimazole therapy, and 13 of them showed relapse of hyperthyroidism. A significant rise of M-Ab with respect to the values observed at the end of treatment occurred in all relapsing patients who had abnormally elevated M-Ab levels before therapy. With one exception, no M-Ab increase was found in the 10 nonrelapsing patients. However, no difference between relapsing and nonrelapsing patients was observed when the M-Ab changes occurring during treatment were considered. A similar trend during and after withdrawal of therapy was noted for Tg-Ab but, because of the relatively small percentage of positive subjects (25%), the results were less conclusive. The present data indicate that methimazole treatment induces a fall of thyroid antibodies in patients with Graves' disease, and that relapse of hyperthyroidism is associated with an increase of these antibodies. However, the antibody changes occurring during treatment showed no prognostic value in predicting the outcome of therapy.

An enzyme immunoassay for the measurement of anti-thyroglobulin autoantibody in human serum

An enzyme-linked sandwich immunoassay using human thyroglobulin conjugated with beta-D-galactosidase and silicone rods coated with human thyroglobulin was developed for the measurement of circulating anti-thyroglobulin autoantibody. The volume of serum needed for the assay was as little as 5 microliter. The sensitivity of the assay was approximately 7 x 10(-15) mol/tube of antithyroglobulin immunoglobulin G corresponding to 220 ng/ml of serum, which was equal to or rather higher than that of radioimmunoassay. The specificity of the assay was demonstrated by (1) parallelism of the standard curve with dilution of sample sera of patients with thyroid diseases, and (2) non-detectability of anti-thyroglobulin in autoantibody in the sera of normal subjects. The precision of the assay was proven by (1) sufficient recovery of antithyroglobulin immunoglobulin G added to serum, and (2) coefficients of variance within and between assays were 6.5 to 10.3% and 4.9 to 14.1%, respectively. No effect of thyroglobulin on the present assay was observed when the ratio of the amount of thyroglobulin to that of anti-thyroglobulin immunoglobulin G was lower than 1 : 10. Furthermore, a significant correlation was observed between anti-thyroglobulin autoantibody concentrations measured by our enzyme immunoassay and those by tanned red cell hemagglutination (r = 0.78), and between those by the enzyme immunoassay and those by radioimmunoassay (r = 0.80). The application to clinical samples ensured the high sensitivity and the adequate validity of the present assay.

Occurrence and natural history of chronic lymphocytic thyroiditis in childhood

In a six-year survey of 5,179 school children in Arizona, Utah, and Nevada 62 cases of chronic lymphocytic thyroiditis were identified giving a prevalence of 1.2%. Thyroids were enlarged in 85%, firm in 60%, and had an irregular or lobulated surface in 75%. Antibodies to thyroglobulin were demonstrable in the serum at some time during the course of the disease in 76% by the tanned red blood cell technique and in 93% by radioimmunoassay. Serum TSH concentrations were elevated in seven of 15 subjects. Many of the cases were early or mild thyroiditis and, in most instances, subjects were asymptomatic and considered clinically euthyroid. Two subjects were hypothyroid, and two appeared clinically hyperthyroid. Spontaneous resolution of thyroiditis occurred in 15 of 32 individuals who received no treatment. Resolution occurred in 14 of 30 children treated with thyroid hormone supplement. The results suggest that lymphocytic thyroiditis in children may be present without symptoms and in many is a self-limiting disorder from which complete recovery occurs spontaneously.